Long persistent phosphor incorporated within a fabric material

ABSTRACT

A process for incorporating a long persistent phosphor into a fabric material which occurs by firing a phosphor whithin a crucible, then grinding the resulting aggregate into a phosphor particulate of specified size, encapsulating the phosphor particulate witthin a water impervious coating material and then applying a specified ratio by weight of the encapsulated phosphor particulates into the fabric material. Further, a fibrous product is described incorporating encapsulated long persistent phosphor particles.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to phosphorescent basedmaterials and, more particularly, to a process and product by processfor incorporating a long persistent phosphor within a fabric material.

[0003] 2. Description of the Prior Art

[0004] Various types of phosphor materials are well known in the art andwhich provide varying degrees of persistent luminescence. A commonobjective of phosphor materials is to provide an application for aluminescent light source which takes advantage of intermittent lightirradiation and/or the absence of irradiating light on a continuousbasis.

[0005] While the existence of phosphor materials such as above is fairlywell known in the art, the recent trend has been to identify usefulapplications of persistent phosphor which will enable the production ofproduction of sufficient light illumination following an iterativeperiod of light irradiation.

SUMMARY OF THE INVENTION

[0006] In order to incorporate a long persistent phosphor into a fabricmaterial a process is detailed of incorporating a long persistentphosphor into a fabric material which occurs by firing a doped phosphor,grinding the resulting phosphor into a phosphor particulate of specifiedsize, encapsulating the phosphor particulate within a water imperviouscoating material and then applying a specified ratio by weight of theencapsulated phosphor particulates to the fiber host material.

[0007] Further, a fibrous product is described incorporatingencapsulated long persistent phosphor particles.

[0008] Also provided is a fibrous product obtainable by the describedprocess of incorporating a long persistent phosphor into a fiber hostmaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Reference will now be made to the attached illustration, whenread in combination with the following detailed description, whereinlike reference numerals refer to like parts throughout the severalviews, and in which:

[0010]FIG. 1 is a schematic of the production of a fabric host materialincorporating the long persistent phosphor according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention is a process, as well as a product producedby a process, for incorporating a long persistent phosphor within afabric host material. A significant number of different fabric fibrousmaterials are capable of being utilized with the phosphorescentmaterial. Without limitation, fibers may include nylon, rayon, man-madefibers, natural fibers such as cotton, wool, jute, linen, silk,polyester fibers, polyalkylene fibers and plastic fibers, cellulose,cellulose acetate, polyamide, acetate, acrylic, polyacrylics, aramid,azlon, modacrylic, nonoloid, nytril, olefin, SPANDEX®, vinal, vinyon,rubber, polybutadiene, composite fibers such as Rhovyl Eco which is acomposite of vinyl fiber and wool manufactured by Rhovyl.

[0012] The long persistent phosphorescent material is constituted by anyof a number of various chemical compositions as are known in the art. Asused herein “long persistence” is defined to mean a phosphorescencelifetime greater than 1 minute. The phosphor is typically provided as apowderized or granulate material and, in one instance, may include alime green phosphor produced under the commercial name Nemoto Luminovaand consisting of a strontium aluminate material. Additional Luminovacolors include blue and which is constituted by a recipe of a CalciumStrontium Aluminate, and which is doped with Europium.

[0013] Other phosphors may specifically include a strontium sulfidematerial which is fired in an inert crucible at a selected elevatedtemperature and for a determined time period. To achieve the desiredlevel of long persistence, as well as a given color, a dopant is addedto the phosphor. While dopant precursors are typically slurried withphosphor precursors prior to firing it is appreciated that dopants arealso intercalated into a phosphor through exposing a fired phosphor to adopant. Post-firing dopant addition illustratively occurs throughsolution surface coating or ion implantation. Experimentation withdifferent dopants has determined that a Europium dopant will achieve apersistent phosphor having an orange/red color. Dopants are typicallypresent from 0.1 to 5 atomic percent. Often it is desirous to include asecond dopant to enhance persistence lifetimes or modify phosphor color.As is also well known in the art, additional types of dopants mayinclude alumina, lanthanum oxide, lanthanides, main group metal cations,fluoride, chloride and bromide and are capable of yielding persistentphosphors having pale yellow and purple shades. Further, the use ofvarying percentages of Calcium with Strontium Sulfide will achieveadditional color shades leading to a purer red color.

[0014] Following the crucible firing of the doped phosphor, thepersistent phosphor composition is dried and is retrieved in a rock-likeform. A subsequent crushing and grinding operation reduces the meanparticle domain size to a preferred range of 1 to 60 microns. Morepreferably, the particle mean domain size is from 1 to 45 microns.Certain applications require particular sizes to be reduced to, in someinstances, less than 1 micron in size. Prior to introducing thephosphorescent particles into a host material, it is desirable to coator encapsulate them so as to ensure its long term performance. It hasbeen found that moisture, over time, tends to degrade the ability of thephosphor to maintain its long-term performance.

[0015] Accordingly, one or more types of encapsulation techniques areemployed to coat the individual phosphor granulates. A first type ofencapsulation is provided by a silicon oxide applied during a firingtemperature of 800° C. A fluoride material may be appliedcontemporaneously with or separately from the silicon oxide. Typically,a firing temperature of approximately 700° C. is best suited forapplication of fluoride. Other encapsulation techniques may employorganic chlorosilanes in hexane or heptane solvents. The process stepsin which the encapsulation of the material is accomplished typicallyincludes mixing the coating powder with the substrate powder in anappropriate ratio, firing the mixed powder at the prescribed temperaturefor a defined time, washing the fired powder to remove the uncoatedportion of the core powder, and drying the washed powder. Still otherencapsulation techniques employ clear water impervious materials to coatthe long persistent phosphor particles. Such materials illustrativelyinclude polyurethane and epoxy-based resins. Additional encapsulationtechniques are illustratively detailed in U.S. Pat. Nos. 4,710,674;5,049,408; 5,196,229; 5,118,529; 5,113,118 and 5,220,341.

[0016] With reference again to the list of fabric materials previouslyrecited, as well as to FIG. 1, the encapsulated phosphor particulate isillustrated at 10. The encapsulated long persistent phosphor 10 isadhered to host fibers 20 prior to the subsequent weaving into a garmentor article. The encapsulated long persistent phosphor can beincorporated into the host material by chemical binding by covalent ornon-covalent bonds. For example, encapsulated long persistent phosphoris coated with silane which confers a positive charge. Fibers having anegative charge will bind the silane-treated encapsulated longpersistent phosphor particles. It is appreciated that the encapsulatinglayer can be derivatized to expose a chemical moiety capable of bindingto a fiber according to the present invention the chemical moietyillustratively including carboxy, carbonyl, hydroxyl, amide, amine,amino, ether, ester, epoxides, cyanate, isocyanate, thiocyanate,sulfhydryl, disulfide, oxide, diazo, iodine, sulfonic or similar groupshaving chemical or potential chemical reactivity. The chemical moietyexposed on the encapsulating layer will be capable of reacting with acomplementary chemical moiety exposed on the fiber, the identity ofwhich will be obvious to one skilled in the art. In another preferredembodiment of the present invention, the encapsulated long persistentphosphor is mixed during the manufacture stage with a settable materialand the settable material encapsulated long persistent phosphor mix isapplied to fibers. Additional techniques for binding encapsulatedparticles to fiber are illustratively detailed in U.S. Pat. No.5,607,759. Encapsulation of the phosphor particulates permits them tomaintain their long persistent and rechargeable characteristics duringsubsequent use and exposure to the environment.

[0017] Any patents mentioned in the specification are indicative of thelevels of those skilled in the art to which the invention pertains.These patents and publications are herein incorporated by reference tothe same extent as if each individual publication was specifically andindividually indicated to be incorporated by reference. Having describedour invention, it will become apparent that it teaches a novel anduseful process and product by process for incorporating a longpersistent phosphor, such as in a particulate form, within a fabric hostmaterial. Fabric host material with the incorporated long persistentphosphor are used to enhance visibility in products such as garments andaccessories worn or carried by safety and rescue personnel, constructionworkers, bikers and children. In addition the material is used toconstruct safety and warning signs and apparatus such as life vests.Many and numerous additional embodiments will become apparent to thoseskilled in the art to which it pertains without deviating from the scopeof the appended claims.

We claim:
 1. A process for incorporating a long persistent phosphorwithin a fabric material, comprising the steps of: firing a dopedphosphor; grinding said doped phosphor into a phosphor particulate ofspecified mean particle domain size; encapsulating said phosphorparticulate within a water impervious coating material; and applying aspecified ratio by weight of said encapsulated phosphor particulates tothe fiber host material.
 2. The process according to claim 1, whereinsaid phosphor is strontium sulfide with a europium dopant.
 3. Theprocess according to claim 1 wherein said doped phosphor furthercomprises a second lanthamide dopant.
 4. The process according to claim1, wherein said phosphor is a mixed calcium strontium sulfide.
 5. Theprocess according to claim 1, wherein said phosphor particulate isencapsulated within a fluoride coating.
 6. The process according toclaim 1, wherein said phosphor particulate is encapsulated within asilicate coating.
 7. The process according to claim 1, wherein saidphosphor particulate is ground to a mean particle domain size of 1 to 60microns.
 8. A fibrous product incorporating encapsulated long persistentphosphor particulate into fiber host material.
 9. The fibrous product ofclaim 7 wherein said fiber host material is selected from the groupconsisting of: synthetic, natural and composite.
 10. The fibrous productof claim 7 wherein said natural fiber host material is selected from thegroup consisting of: cotton, wool, jute, linen, silk, hemp and rubber.11. The fibrous product of claim 7 wherein said synthetic fiber hostmaterial is selected from the group consisting of: nylon, rayon,plastic, cellulose, cellulose acetate, polyamide, acetate, acrylic,polyacrylics, aramid, azlon, modacrylic, nonoloid, nytril, olefin,saran, spandex, vinal, vinyon, polyester, polyethylene andpolybutadiene.
 12. The fibrous product of claim 8 where saidencapsulated long persistent phosphor particulate is incorporated at0.1-30 weight/volume percent.
 13. The fibrous product of claim 8 wheresaid encapsulated long persistent phosphor particulate is incorporatedat 5-25 weight/volume percent.
 14. The fibrous product of claim 8 wheresaid encapsulated long persistent phosphor particulate is incorporatedat 10-20 weight/volume percent.
 15. The fibrous product of claim 8wherein said phosphor particulate is ground to a mean particle domainsize of 1 to 60 microns.
 16. The fibrous product of claim 8 wherein saidphosphor particulate is ground to a mean particle domain size of 1 to 45microns.
 17. The fibrous product of claim 8 where said long persistentphosphor is strontium sulfide with a dopant.
 18. The dopant of claim 15where said dopant is europium.
 19. The encapsulated long persistentphosphor of claim 8 wherein a chemical moiety is present.
 20. Thechemical moiety of claim 17 where said moiety is derivatized to areactive group selected from the group consisting of: carboxy, carbonyl,hydroxyl, amide, amine, amino, ether, ester, epoxides, cyanate,isocyanate, thiocyanate, sulflhydryl, disulfide, oxide, diazo, iodineand sulfonic.
 21. A fibrous product as claimed in claim 7 obtainable bythe process of claim 1